“Daryl Williams dislocated his right patella and tore the medial collateral ligament in his right knee in this morning’s practice,” Vermillion said in a statement released by the team. “We are beginning the early stages of rehabilitation, and there is currently no timetable for his return.”

Panthers coach Ron Rivera said it was difficult for players to resume practice after watching what happened.

"We were kind of floating right there, especially on the offensive side," he said. "You could feel it and it takes a little wind out of your sails a little bit. But after that period we refocused."

Williams was engaged with two pass rushers during 11-on-11 team drills at Wofford College when his knee bent back awkwardly. Several players gathered around Williams and others took a knee while the crowd went silent.

Williams, entering his contract season, has started 28 games and played in 39 during his three seasons in Carolina. He started all 16 games at right tackle last season.

Pro Football Focus ranked Williams as top right tackle in the NFL last season and the third-best offensive tackle overall.